Currently, audio power amplifiers have high output power and high output current, it is easy to burn out when large current flows transistors of the power amplifier for a long time, especially when short-circuit status occurs. In the course of using, the output of power amplifier may be shorted to power supply line, ground wire, and loads due to improper operation. Using a single short-circuit protection method, the power amplifier may he power-on or power-off alternately or shocked by large current repeatedly, reducing its life and reliability. At present, there are three main short-circuit protection methods for power amplifier: 1) self-locking short-circuit protection is to lock the power amplifier after the power amplifier has short-circuit status, and the power amplifier does not output. The power amplifier does not return to operation even after the short-circuit fault is eliminated. The power amplifier can return to operation when it is restarted. 2) continuous short-circuit protection is to continuously detect the output of the power amplifier after the power amplifier has short-circuit status, and control the transistors of the power amplifier to be turned on or off according to the detection result. The power amplifier can return to operate after the short-circuit fault is eliminated. 3) blanking self-locking short-circuit protection is to detect the output of power amplifier after the power amplifier has short-circuit status, and control the transistors of the power amplifier to be turned on or off repeatedly according to the detection result, at the same time, it calculate the number of short-circuit or short circuit time. When the number of short-circuit or short circuit time is larger than a preset value, the power amplifier does not output, to avoid shocking the transistors of the power amplifier and prevent the power amplifier from being turned off by mistake triggering of the short-circuit.
However, there are different disadvantages in the three methods, such as self-locking short-circuit protection can return to operate through restarting after the power amplifier has short-circuit status. This method cannot avoid shutting the power amplifier by instantaneous short-circuit caused by human error. The continuous short-circuit protection can avoid shutting the power amplifier by instantaneous short-circuit caused by human error. The power amplifier can return to operate after the short-circuit fault is eliminated. However, this method makes the transistors of the power amplifier in an over-current status or protection status, which will adversely affect life and reliability of the power amplifier. The blanking self-locking short-circuit protection can prevent the transistors of the power amplifier from being over-current, but the protection behavior is single in different situations, such as the output of the power amplifier has short-circuit status with the power supply line, the ground wire, or the loads. When the short-circuit status occurs, the power amplifier are locked after the large current reaches a preset value in a preset time, and then, the power amplifier can return to operate through restarting.